KR20170135384A - Apparatus for distributed clock synchronization based on EtherCAT, method thereof and computer recordable medium storing the method - Google Patents

Abstract

The present invention relates to an apparatus for distributed clock synchronization based on Ethernet for control automation technology (EtherCAT), capable of correcting a measurement error of a propagation delay; a method thereof; and a computer-recordable medium storing the same. According to the present invention, the apparatus comprises: a communication unit connected to a slave device including a reference slave device and at least one common slave device through an EtherCAT network to perform communication; a delay time calculation module to calculate a propagation delay time of the common slave device when a system or control application is re-executed; an average delay calculation module using the calculated propagation delay time and a previously calculated exponential weight moving average (EWMV) to calculate a current EWMV; and a delay time recording module transmitting the calculated current EWMV through the communication unit to allow the common slave device to record the calculated current EWMV in a register as the propagation delay time.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for synchronizing distributed clocks based on an Ethernet, a method therefor, and a computer readable recording medium on which the method is recorded.

The present invention relates to an Ethernet-based distributed clock synchronization technique, and more particularly to an apparatus for an Ethernet-based distributed clock synchronization capable of correcting a propagation delay measurement error, a method therefor and a computer Readable recording medium.

Thanks to IT trends, existing control systems are quickly replacing distributed control systems using industrial Ethernet technology. Industrial Ethernet technology is defined as a standard such as IEC 61784, 61158-2, and enables efficient configuration of a distributed control system by utilizing various advantages such as high transmission rate, TCP / IP support, and cost competitiveness. In particular, EtherCAT, one of the industrial Ethernet standards, is actively used in precision control systems in various fields by realizing high-speed real-time communication through an integrated message frame and hardware-based frame relay.

EtherCAT messages to be transmitted to multiple devices in the network are bundled into one Ethernet frame, so that a very high transmission bandwidth can be realized. Also, since each device transmits the received frame to the next device through hardware-based frame relay, a highly deterministic message transmission time can be secured and a highly synchronized distributed control system can be constructed. Accordingly, EtherCAT is applied to various control applications such as factory automation, robot surgery, and production process.

Precise clock synchronization is becoming increasingly important in distributed control systems. In the case of determining the task cycle in the control device depending on the local clock without performing the clock synchronization in the distributed control network, it is difficult to implement the synchronized operation since the task activation time of all devices belonging to the control network is not constant. On the other hand, using a globally synchronized clock enables a high level of synchronous control. For example, in the case of industrial robots, the desired path can be tracked precisely by controlling the motor by synchronizing the motor drive.

Korea Publication No. 2014-0014918 Published Feb. 06, 2014 (name: Ethernet communication system and time synchronization method)

An object of the present invention is to provide an apparatus for an Ethernet-based distributed clock synchronization capable of correcting a propagation delay measurement error caused by a propagation delay deviation, a method therefor, and a computer readable recording medium on which the method is recorded .

According to another aspect of the present invention, there is provided an apparatus for synchronizing distributed clocks of a master device, comprising: a slave device including a reference slave device and at least one common slave device; And a control unit for controlling the control unit so as to calculate a propagation delay time of the common slave unit when the system application or the control application is executed again; And calculating a current exponentially weighted moving average by using the weighted moving average; and calculating a current exponentially weighted moving average by using the calculated current exponent moving average so that the common slave device records the calculated exponentially weighted moving average in a register The weighted moving average is transmitted through the communication unit And a delay time recording module.

Wherein the current exponential weighted moving average is an average of a value obtained by applying a weight to the calculated propagation delay time when the system application or control application is re-executed and an average of a value obtained by applying a residual weight to the previously calculated exponential weighted moving average .

The current exponentially weighted moving average is calculated by the following equation

는 현재의 지수 가중 이동 평균이며, 상기

은 초기 지수 가중 이동 평균이고, 상기

는 가중치이며, 상기

는 현재 산출된 전파 지연 시간이고, 상기

는 상기 이전에 산출된 지수 가중 이동 평균인 것을 특징으로 한다. Is calculated according to the equation

Is the current exponentially weighted moving average,

Is an initial exponential weighted moving average,

Is a weight,

Is the currently calculated propagation delay time,

Is the previously calculated exponentially weighted moving average.

Further, when the delay time calculation module detects that the network is configured, it calculates the propagation delay time of the common slave device a plurality of times, and the delay average calculation module calculates an average of the propagation delay times calculated the plurality of times, As a weighted moving average.

According to another aspect of the present invention, there is provided a method for an EDC based distributed clock synchronization of a master device, wherein when a system application or a control application is re-executed, a reference slave device and at least one common slave device Calculating a current exponential weighted moving average using the calculated propagation delay time and a previously calculated exponential weighted moving average; And transmitting the calculated current exponentially weighted moving average to the register so that the common slave device records the calculated exponentially weighted moving average as a propagation delay time.

Here, the current exponential weighted moving average may be an average of a value obtained by applying a weight to the calculated propagation delay time when the system application or the control application is re-executed and an average of a value obtained by applying a residual weight to the previously calculated exponential weighted moving average .

In other words, the current exponential weighted moving average is calculated by the following equation

는 현재의 지수 가중 이동 평균이며, 상기

은 초기 지수 가중 이동 평균이고, 상기

는 가중치이며, 상기

는 현재 산출된 전파 지연 시간이고, 상기

는 상기 이전에 산출된 지수 가중 이동 평균인 것을 특징으로 한다. Is calculated according to the equation

Is the current exponentially weighted moving average,

Is an initial exponential weighted moving average,

Is a weight,

Is the currently calculated propagation delay time,

Is the previously calculated exponentially weighted moving average.

When the network is configured, the propagation delay time of the common slave device is calculated a plurality of times, and the initial exponential weighted moving average is an average of the propagation delay times calculated a plurality of times.

According to another aspect of the present invention, there is provided a computer-readable recording medium on which is recorded a method for an EDC-based distributed clock synchronization of a master device according to a preferred embodiment of the present invention.

According to the present invention, when configuring a network, when a system or a control application is re-executed, the propagation delay is measured as many times as necessary, the exponentially weighted moving average is calculated through the measured propagation delay, So that accurate distributed clock synchronization can be achieved with an appropriate number of operations.

1 and 2 are views for explaining a configuration of an Ethernet-based distributed control system according to an embodiment of the present invention.
3 is a block diagram for explaining a master device according to an embodiment of the present invention.
4 and 5 are views for explaining a method for distributed clock synchronization according to an embodiment of the present invention.
6 and 7 are flowcharts illustrating a method for distributed clock synchronization according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Note that, in the drawings, the same components are denoted by the same reference symbols as possible. Further, the detailed description of known functions and configurations that may obscure the gist of the present invention will be omitted. For the same reason, some of the elements in the accompanying drawings are exaggerated, omitted, or schematically shown, and the size of each element does not entirely reflect the actual size.

In particular, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings, and the inventor should understand the concept of the term The present invention should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents It should be understood that water and variations may be present.

First, an EtherCAT-based distributed control system according to an embodiment of the present invention will be described. 1 and 2 are views for explaining a configuration of an Ethernet-based distributed control system according to an embodiment of the present invention.

Referring to FIGS. 1 and 2, a distributed control system according to an embodiment of the present invention includes a master device 100 and a plurality of slave devices 200. As an example, the plurality of slave devices 200 may be motor drivers for controlling motors disposed on the axis of one of the robot arms, as shown in Fig. The master device 100 may be a device capable of performing a computer operation for controlling each motor driver.

The slave device 200 can be divided into a reference slave device 210 and one or more common slave devices 220. The reference slave device 210 is the slave device 200 located first in relation to the master device 100 on the network topology of the Ethernet-based distributed control system. The common slave device 220 refers to the slave device 200 other than the reference slave device 210.

The configuration of the master device 100 according to the embodiment of the present invention will now be described. 3 is a block diagram for explaining a master device according to an embodiment of the present invention. Referring to FIG. 3, the master device 100 includes a communication unit 110, a storage unit 120, and a control unit 130.

The communication unit 110 is for communicating with the slave device 200 when the master device 100 and a plurality of slave devices 200 are connected via the Ethernet network. The communication unit 110 may transmit and receive datagrams to the slave device 200. A datagram is a basic message unit of the Ethernet, and a datagram can write data to or read data from a memory (or a register) having a specific address of the slave device 200 designated. The datagrams transmitted are contained in one Ethernet frame and transmitted.

The datagrams are generated periodically by the master device 100 and sequentially transmitted to all the slave devices 200, and are transferred from the last slave device 200 in the reverse order to the master device 100 again. When the datagram reaches the destination slave device 200, the necessary data is read from the memory of the slave device 200 or the data to be written is copied. The distributed control system preferably uses a network topology of a ring type, and can share clock values among all devices through a datagram.

The storage unit 120 may be implemented as a memory or a register. The storage unit 120 may store an exponentially weighted moving average calculated by the controller 130 or a weight used when the exponentially weighted moving average is calculated.

The controller 130 may control the overall operation of the master device 100 according to an embodiment of the present invention and the signal flow between the internal blocks of the master device 100 and may perform a data processing function for processing the data. The controller 350 may represent a central processing unit (CPU). The controller 130 according to the embodiment of the present invention includes a delay time calculating module 131, a delay average calculating module 133, and a delay time recording module 135. The operation of the controller 130 including the delay time calculation module 131, the delay average calculation module 133 and the delay time recording module 135 will be described in more detail below.

The master device 100 includes an input unit (not shown) for inputting a user's input to the master device 100, a display unit (not shown) for displaying status information about the slave device 200 to which the master device 100 is connected And the like). However, the description thereof will be omitted for the sake of simplicity.

Next, a method of performing distributed clock synchronization according to an embodiment of the present invention will be described. 4 and 5 are views for explaining a method for distributed clock synchronization according to an embodiment of the present invention.

Before describing the detailed method, the terms used in distributed clock synchronization will be described. For distributed clock synchronization, you can use the terms defined in the standard document as follows: The system time is a time for displaying the global clock value, which is defined as an integer value incremented by 1 nanosecond from the midnight of January 1, 2000. The system time is stored in a 64-bit register for each slave device 200, and is managed by a clock synchronization function according to an embodiment of the present invention. The local time represents a time unique to the slave device 200 and is managed by a local clock (slave clock) built in the slave device 200. [ The reference time indicates the system time managed by the slave device 200 closest to the master device 100, i.e., the reference slave device 210, and the system time of all the slave devices 200 indicates a reference time Synchronized.

The distributed control system according to the embodiment of the present invention can synchronize the clocks of all devices in the network through the following three aspects: offset correction, propagation delay correction and drift compensation have. The offset refers to the difference between the reference time and the local time. And the start time difference of the local time caused by the difference in boot time of each slave device 200 and the like. Propagation delay means a time required for message transmission from the master device 100 to each slave device 200. The propagation delay may vary depending on the type of the network topology, the implementation characteristics of the slave device 200, and the position of the slave device 200 in the network. The system time drift refers to the difference in system time due to the oscillation deviation of the oscillator generated in the local clock of each slave device 200.

Even if the system time of each slave device 200 is exactly synchronized, an error occurs due to drift. Clock synchronization is accomplished through the following three steps: propagation delay measurement, offset correction, and drift correction.

를 슬레이브 장치 s의 포트 p에 측정 프레임이 도착한 시간으로 정의하였을 때, 슬레이브 장치 i, i+1 사이의 전파 지연 시간은 다음의 수학식 1과 같다. The propagation delay measurement is performed when the master device 100 initializes the slave device 200. To measure the propagation delay, the master device 100 transmits a global write (BWR) command for a register of a specific address to all the slave devices 200 in a frame. Each slave device 200 measures the time when the command is received on the basis of the local time and stores it in the corresponding register. The time at which the frame that circulates and returns to all the slave devices 200 arrives at each port is also recorded in the corresponding register. When the recording of each arrival time is completed, the master device 100 reads the corresponding register value from all the slave devices 200. The master device 100 can measure the propagation delay from the read time value. Referring to Figure 2,

Is defined as the arrival time of the measurement frame at the port p of the slave device s, the propagation delay time between the slave devices i and i + 1 is expressed by the following equation (1).

As described above, the master device 100 can measure the propagation delay time between each of the slave devices 200, and calculate the propagation delay time between the reference slave device 210 and each common slave device 220. The calculated propagation delay time is recorded by the master device 100 in a corresponding register of each slave device 200, for example, a "system time delay" register.

The system time of the reference slave device 210 is transferred to the common slave device 220 under the control of the master device 100 during the initialization of the slave device 200 for offset correction. Then, the common slave device 220 calculates a difference between the received system time and its local time and stores the difference in a corresponding register, for example, a "system time offset" register. This is expressed by the following equation (2).

The drift correction is performed in the operation (OP) state of the master device 100. The master device 200 must periodically transmit the reference time value to each slave device 200 for drift correction. To this end, the master device 200 may use a "Read Multiple Write (RMW)" More specifically, when transmitting an EtherCAT frame for real-time communication with the slave device 200, the master device 200 transmits a frame including a correction datagram together with a datagram containing real-time data at a predetermined drift correction period . At this time, the master device 200 reads the system time of the reference slave device 210, and then includes the read system time in the correction datagram. Accordingly, the system time is transmitted to each common slave device 220 via the correction datagram. At this time, the common slave device 220 receiving the system time calculates its own system time drift based on the following Equation (3).

As described above, after calculating the drift, the common slave device 220 can correct the local clock speed of the common slave device 220. If the drift has a positive value, it means that the speed of the system time managed by the common slave device 220 is faster, thereby reducing the speed of the local clock and reducing the drift. In the opposite case, the speed of the local clock can be increased to reduce drift.

In the propagation delay measurement, the propagation delay is determined by a wire propagation delay proportional to the cable length from the reference slave device 210 to the slave device 220, a total propagation delay that is proportional to the cable length from the reference slave device 210 to the slave device 220, Processing delays of the slave devices 200, and fowarding delays in the hardware or software frame relay for the slave devices 220 to transfer frames. Due to the above-described processing delay and propagation delay, the propagation delay measured for each frame may have a deviation. This propagation delay deviation may be reflected in the propagation delay measurement value for each common slave device 220. The system time of the common slave device 220 can be maintained constant according to the measurement error due to the propagation delay deviation. In addition, during the process of receiving the system time of the reference slave device 210 in the offset correction step, the propagation delay deviation may be reflected as an error in the offset calculation. Since the propagation delay deviation is accumulated each time the slave device passes, the propagation delay deviation may become larger as the number of the slave devices increases, so that the initial offset error can also be increased.

A method for the distributed clock synchronization for correcting the influence due to the propagation delay deviation will now be described. 6 and 7 are flowcharts illustrating a method for distributed clock synchronization according to an embodiment of the present invention. Although only one common slave device 220 will be shown and described in the embodiment with reference to Figures 6 and 7, as in the embodiment shown in Figure 1, there can be a plurality of common slave devices 220, The present invention may be applied to a distributed control system composed of a plurality of common slave devices 220, as long as those skilled in the art are familiar with the present invention.

Referring to FIG. 6, the delay time calculation module 131 of the master device 100 may recognize that the network is initially or newly configured in step S110. Then, in step S120, the delay time calculation module 131 of the master device 100 measures the propagation delay time through the reference slave device 210 and the common slave device 220, and calculates the propagation delay time. Step S120 includes steps S121 to S131, and step S120 is performed a plurality of times.

Step S120 will be described in detail as follows. The delay time calculation module 131 of the master device 100 transmits a frame for propagation delay measurement in step S111 through the communication unit 110. [ This frame will be referred to as a measurement frame. The measurement frame includes a BWR (Broadcast Write) command. The measurement frame transmitted to the step S111 by the delay time calculation module 131 of the master device 100 circulates through all the slave devices 200 and returns to the master device 100 again. That is, the measurement frame is transmitted from the reference slave device 210 to the common slave device 220 in step S123, transferred from the common slave device 220 to the reference slave device 210 in step S125, And transferred from the device 210 to the master device 100. Referring to FIG. 2, when the measurement frame traverses the slave devices 210 and 220 in the network, each slave device 210 and 220 determines the arrival time of a frame for each port (Port 0 and Port 1) . When the delay time calculation module 131 of the master device 100 receives the measurement frame again, it is determined that the measurement is completed.

Accordingly, the delay time calculation module 131 collects measured frame arrival times from the reference slave device 210 and the common slave device 220 in step S129. Then, the delay time calculation module 131 of the master device 100 calculates the frame propagation delay time in the network according to the network topology of the slave device 200 in step S131. For example, the delay time calculation module 131 of the master device 100 can calculate the propagation delay time according to Equation (1).

). 이는 아래의 수학식 4를 참조로 상세하게 설명될 것이다. 그런 다음, 마스터 장치(100)의 지연시간기록모듈(135)은 S150 단계에서 산출된 전파 지연 시간의 평균을 전파 지연 시간으로 커먼 슬레이브 장치(220)의 레지스터에 기록한다. 이때, 지연시간기록모듈(135)은 통신부(110)를 통해 앞서 산출된 전파 지연 시간의 평균이 전파 지연 시간으로 기록된 데이터그램이 포함된 프레임을 커먼 슬레이브 장치(220)로 전송하면, 커먼 슬레이브 장치(220)는 수신된 전파 지연 시간의 평균을 전파 지연 시간으로 해당 레지스터에 기록할 수 있다. 이에 따라, 적어도 하나의 커먼 슬레이브 장치(220)는 기록된 전파 지연 시간의 평균을 전파 지연 시간으로 하여 분산 시계를 동기화할 수 있다. Step S110 is performed a plurality of times, whereby a plurality of propagation delay times can be calculated. Accordingly, the delay average calculation module 133 of the master device 100 obtains the average of the plurality of propagation delay times calculated in the step S140. Here, the average of the calculated plurality of propagation delay times may be an initial exponentially weighted moving average (

). This will be described in detail with reference to Equation (4) below. Then, the delay time recording module 135 of the master device 100 records the average of the propagation delay time calculated in step S150 in the register of the common slave device 220 as the propagation delay time. At this time, when the delay time recording module 135 transmits a frame including the datagram in which the average of the propagation delay time calculated in advance through the communication unit 110 is recorded as the propagation delay time, to the common slave device 220, The device 220 may record the average of the received propagation delay time in the corresponding register as the propagation delay time. Accordingly, at least one common slave device 220 can synchronize the distributed clock by setting the average of the recorded propagation delay time as the propagation delay time.

As described above, according to one embodiment, the propagation delay time is an average of the propagation delay time. In this state, the master device 100 updates the propagation delay time, as shown in Fig. 5, whenever the system or control application is re-executed. Referring to FIG. 7, the delay time calculation module 131 of the master device 100 may recognize that the system application or the control application is executed again in step S220.

Then, in step S220, the delay time calculation module 131 of the master device 100 measures the propagation delay time through the reference slave device 210 and the common slave device 220, and calculates the propagation delay time. Step S220 includes steps S221 to S231, and step S220 is performed once. In operation S220, the same operation as in operation S120 is performed, and operations S221 to S231 included in operation S220 are performed in the same manner as operation S121 through operation S131. That is, in steps S211 to S231, the measurement frames are returned to the master device 100 by circulating through all the slave devices 200. [ At this time, when this measurement frame traverses the slave devices 210 and 220 in the network, each of the slave devices 210 and 220 measures the arrival time of the frame for each port (Port 0, Port 1) 2). When the delay time calculation module 131 of the master device 100 receives the measurement frame again through the communication unit 110, it is determined that the measurement is completed.

Accordingly, the delay time calculation module 131 of the master device 100 collects the measured frame arrival times from the reference slave device 210 and the common slave device 220 in step S229. Then, the delay time calculation module 131 of the master device 100 calculates the frame propagation delay time between nodes in the network according to the network topology of the slave device 200 in step S231 (Equation 1).

Since step S220 is performed once, one propagation delay time is calculated. Accordingly, the delay average calculation module 133 of the master device 100 obtains an exponential weighted moving average (EWMA) of the propagation delay time in step S240. This exponentially weighted moving average is calculated according to the following equation (4).

는 현재의 지수 가중 이동 평균이며,

은 초기 지수 가중 이동 평균이며, 초기 지수 가중 이동 평균은 도 4를 참조로 하는 실시예에 따라 산출되는 복수의 전파 지연 시간의 평균이 될 수 있다.

는 가중치이며,

는 현재 산출된 전파 지연 시간이고,

는 이전에 산출된 지수 가중 이동 평균이다. 즉, 수학식 4의 (현재의) 지수 가중 이동 평균은 새로 산출된 전파 지연 시간

에 가중치

를 적용한 값과 이전에 산출된 지수 가중 이동 평균

에 잔여 가중치(1-

)를 적용한 평균값이다. 다른 말로, (현재의) 지수 가중 이동 평균

는 시스템 애플리케이션 혹은 제어 애플리케이션이 재실행될 때 새로 산출된 전파 지연 시간

에 가중치

를 적용한 값과 이전에 산출된 지수 가중 이동 평균

에 잔여 가중치 (1-

)를 적용한 값의 평균이다. here,

Is the current exponentially weighted moving average,

Is an initial exponential weighted moving average, and the initial exponential weighted moving average may be an average of a plurality of propagation delay times calculated according to an embodiment with reference to FIG.

Is a weight,

Is the currently calculated propagation delay time,

Is the exponentially weighted moving average calculated previously. That is, the (current) exponentially weighted moving average of Equation (4) represents the newly calculated propagation delay time

Weight

And the previously calculated exponentially weighted moving average

Lt; RTI ID = 0.0 > 1-

). In other words, the (current) exponentially weighted moving average

A new propagation delay time when the system application or control application is re-executed

Weight

And the previously calculated exponentially weighted moving average

Lt; RTI ID = 0.0 > 1-

) Is applied.

As described above, after calculating the exponentially weighted moving average, the delay time recording module 135 of the master device 100 calculates the exponentially weighted moving average calculated in step S250 as the propagation delay time, . At this time, when the delay time recording module 135 transmits to the common slave device 220 a frame including the datagram in which the exponentially weighted moving average calculated in advance through the communication unit 110 is recorded as the propagation delay time, The mobile station 220 may record the received exponentially weighted moving average as a propagation delay time in a corresponding register. Accordingly, at least one common slave device 220 can synchronize the distributed clock with the recorded exponentially weighted moving average as the propagation delay time.

)를 반영하고, 기존 지수 가중 이동 평균에 잔여 가중치(1-??

)를 반영한다. 마스터 장치(100)는 구비된 영구 저장장치(예컨대, flash rom 등)에 해당 네트워크 토폴로지에 대한 지수 가중 이동 평균

과 가중치

를 저장할 수 있다. 한편, 마스터 장치(100)는 도 4에 보인 바와 같이, 네트워크 내 슬레이브 장치(200)의 네트워크 토폴로지가 변경될 경우, 이를 감지하여 새로이 전파 지연 시간을 측정할 수 있다. As described above, the master device 100 sets the propagation delay time average (initial exponentially weighted moving average) as the propagation delay time through multiple measurements only in the initial configuration of the new network topology, and then the system application or control application And calculates one propagation delay time each time it is re-executed. The newly calculated propagation delay time is weighted considering system characteristics (

), And the residual weight (1-?

). The master device 100 may provide an exponentially weighted moving average (for example,

And weight

Can be stored. 4, when the network topology of the slave device 200 in the network is changed, the master device 100 can detect the network topology and measure a new propagation delay time.

Meanwhile, the method according to the embodiment of the present invention described above can be implemented in a form of a program readable by various computer means and recorded in a computer-readable recording medium. Here, the recording medium may include program commands, data files, data structures, and the like, alone or in combination. Program instructions to be recorded on a recording medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. For example, the recording medium may be a magnetic medium such as a hard disk, a floppy disk and a magnetic tape, an optical medium such as a CD-ROM or a DVD, a magneto-optical medium such as a floppy disk magneto-optical media, and hardware devices that are specially configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions may include machine language wires such as those produced by a compiler, as well as high-level language wires that may be executed by a computer using an interpreter or the like. Such a hardware device may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

While the present invention has been described with reference to several preferred embodiments, these embodiments are illustrative and not restrictive. It will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.

100: Master device 110:
120: storage unit 130:
131: delay time calculating module 133: delay average calculating module
135: delay time recording module 200: slave device
210: Reference slave device 220: Common slave device

Claims (3)

An apparatus for use in an ether-based distributed clock synchronization of a master device,
A communication unit connected to a slave device including a reference slave device and at least one common slave device through an EtherCAT network;
A delay time calculation module for calculating a propagation delay time of the common slave device when the system application or the control application is re-executed;
A delay averaging module for calculating a current exponentially weighted moving average using the calculated propagation delay time and the previously calculated exponentially weighted moving average; And
And a delay time recording module that transmits the calculated current exponentially weighted moving average through the communication unit so that the common slave device records the calculated current exponentially weighted moving average as a propagation delay time in the register Device for distributed clock synchronization of an ethercat based master device. A method for an Ethernet-based distributed clock synchronization of a master device,
Calculating a propagation delay time of the common slave device among the slave devices including the reference slave device and the at least one common slave device when the system application or the control application is re-executed;
Calculating a current exponentially weighted moving average using the calculated propagation delay time and a previously calculated exponentially weighted moving average; And
And transmitting the calculated current exponentially weighted moving average to the register so that the common slave device records the calculated exponentially weighted moving average as a propagation delay time. Method for distributed clock synchronization. A computer-readable recording medium on which is recorded a method for the Ethernet-based distributed clock synchronization of a master device according to claim 2.

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